Field watch apparatus

ABSTRACT

A field watch apparatus uses a storage unit to store detection data of a detected obstacle from an obstacle sensor that detects objects under control of a control unit, and the detection data accumulated in the storage unit over time is used to display a mark on a captured image that is captured by a camera and shown on a screen of a display unit. The mark size and other attributes of the mark in the image are controlled in a manner that enables a view to easily recognize an old mark from a new one, thereby providing an intuitive recognition of the obstacle movement in a certain direction in the captured image, when the mark is superposed in the captured image for multiple times based on the accumulated detection data in the storage unit.

CROSS REFERENCE TO RELATED APPLICATION

The present application is based on and claims the benefit of priorityof Japanese Patent Applications No. 2008-310108, filed on Dec. 4, 2008,and No. 2008-310109, filed on Dec. 4, 2008, the disclosures of which areincorporated herein by reference.

FIELD OF THE INVENTION

The present disclosure generally relates to a field watch apparatus thatdetects and displays an obstacle around a vehicle.

BACKGROUND INFORMATION

Conventionally, an obstacle detected by an apparatus was displayed, on ascreen of the apparatus, as a captured image that captures a fieldaround a vehicle, for notifying the user of the danger of the obstacle,for example.

Further, in recent years, the captured image of the obstacle in the nearfield has detection information superposed thereon when it is displayedon the screen. For example, as disclosed in a Japanese patent documentJP-A-2005-45602, the detection information detected by an obstacledetector is translated into a symbolic icon, and the symbolic icon issuperposed in the camera captured image of the near field for thedisplay on a monitoring device.

However, the above technique of the obstacle detection has a problemthat the user has difficulty in determining which way the obstacle ismoving in the captured image. More practically, in the technique in thedocument JP-A-2005-45602, the detection information is displayed in asuperposing manner on the detected obstacle in the captured image onlyas a symbolic icon that shows a detected distance of the obstacle and aposition of the obstacle in a detection area of the detector. Therefore,the user has a hard time to understand whether, for example, theobstacle is moving away from the user's vehicle or is coming closer tothe vehicle, thereby having difficulty in finding which way he or sheshould maneuver.

SUMMARY OF THE INVENTION

In view of the above and other problems, the present disclosure providesa field watch apparatus that enables the user to easily distinguish themoving direction of the obstacle in a near field of the vehicle, whenthe apparatus detects and displays the obstacle in the captured image ofthe near field on a display device or the like.

In an aspect of the present disclosure, the field watch apparatusincludes: an image capture unit for capturing a field image around avehicle: an obstacle detector for detecting an obstacle around thevehicle; a display unit for displaying the field image captured by theimage capture unit; a data acquisition unit for continually acquiringobstacle data from the obstacle detector after an initial detection ofthe obstacle; a storage unit for accumulating the obstacle datacontinually acquired by the data acquisition unit; and a change unit forchanging, in association with the obstacle data, an obstacle mark, whichis superposed on the field image when the obstacle is detected by theobstacle detector. Further, the change unit displays multiple obstaclemarks on the field image based on multiple pieces of the obstacle datain the storage unit, and the obstacle mark representing an older pieceof obstacle data is changed from the obstacle mark representing a lessolder piece of obstacle data for the ease of distinction in the fieldimage. In other words, the shape of the obstacle mark is changed fortime difference between respective data acquisition times of themultiple pieces of obstacle data.

In this manner, the movement of the detected obstacle can bedistinctively displayed in the captured image by the multiple obstaclemarks superposed in the obstacle image. That is, the obstacle marksrepresenting the moving direction of the obstacle enable the user toeasily and intuitively understand the movement of the obstacle relativeto the subject vehicle, when the obstacle is detected in the near fieldof the vehicle.

Further, when the obstacle detection is performed by using anelectro-magnetic wave or a sound wave, the size of the obstacle mark inthe captured image is controlled to be in proportion to the magnitude ofa reflection wave from the obstacle.

The magnitude of reflection wave from the obstacle is basically inproportion to the size and distance of the obstacle. Therefore, by usingthe above operation scheme, the obstacle size can be represented in thecaptured image as the size of the obstacle mark, thereby enabling theuser to easily distinguish the obstacle size.

In other words, both of the movement direction of the obstacle and thesize of the obstacle can be intuitively notified by the arrangement ofthe obstacle marks. Therefore, the user can easily understand, forexample, how close the vehicle currently is to the obstacle by viewingthe captured image.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block diagram showing a schematic configuration of a fieldwatch apparatus in an embodiment of the present invention;

FIG. 2 is an illustration of sensor arrangement and camera capture areain the embodiment of the present invention;

FIG. 3 is a flow diagram showing an obstacle detection process by acontrol unit in the embodiment of the present invention;

FIG. 4 is a flow diagram showing a flow of a superposing process by thecontrol unit in the embodiment of the present invention;

FIG. 5 is an illustration of detection area axes shown in the capturedimage in the embodiment of the present invention;

FIGS. 6A to 6C are illustrations of superposed images that have marks inthe captured image in the embodiment of the present invention;

FIG. 7A to 7C are other illustrations of superposed images that havemarks in the captured image in the embodiment of the present invention;and

FIG. 8 is a flow diagram of a modified flow of the obstacle detectionprocess by the control unit in the embodiment of the present invention.

DETAILED DESCRIPTION

An embodiment of the present invention is explained with reference tothe drawings. FIG. 1 is a block diagram showing a total configuration ofa field watch apparatus 100 to which the present invention is applied.The field watch apparatus 100 shown in FIG. 1 is installed in a vehicle,and includes an obstacle sensor 1, a camera 2, a display 3, a controlunit 4 and a storage device 5. These components are inter-connected by avehicle LAN that uses a communication protocol such as CAN (ControllerArea Network) or the like. In the following, a vehicle carrying thefield watch apparatus 100 is called as an own vehicle.

The obstacle sensor 1 detects an obstacle around the vehicle, or morespecifically, an obstacle in the rear of the vehicle. Therefore, theobstacle sensor 1 functions as an obstacle detector mentioned later inthe claims. For example, the obstacle sensor 1 is installed in the rearbumper of the vehicle, for detecting an obstacle in the rear field ofthe vehicle.

In the present embodiment, four pieces of ultrasound wave sensors areimplemented as the obstacle sensor 1. That is, the ultrasound wavesensors US1 to US4 are installed in the vehicle rear as shown in FIG. 2s. The ultrasound wave sensors US1 to US4 transmit an ultrasound wave,and receive the reflection wave for detecting a distance to an obstacle.In addition, the ultrasound wave sensors US1 to US4 output, to thecontrol unit 4, information of the alternate pulse signal of transmittedultrasound wave, which is designated as transmitted pulse signal, andinformation of the alternate pulse signal of received reflection wave,which is designated as received pulse signal. For example, each of theultrasound wave sensors US1 to US4 transmits the ultrasound wave in turnat a regular interval of, for example, 50 milliseconds, which sets awave transmission cycle starting from the sensor US1, then sensor US2,then sensor US3, to sensor US4, before returning to US1, under controlof the control unit 4. In the following description, the wavetransmission cycle from the sensor US1 to the sensor US4 is designatedas one set of wave transmission cycle.

The camera 2 is installed in the rear of the vehicle, and captures afield in the rear of the vehicle. Therefore, the camera 2 functions asan image capture unit mentioned later in claims. In addition, the camera2 outputs image data around a rear part of the vehicle to the controlunit 4. Further, the camera 2 is installed to capture each of fourdetection areas of the ultrasound wave sensors US1 to US4 in its imagecapture range.

The display 3 displays a captured image based on an image captured bycamera 2. Therefore, the display 3 functions as a display unit mentionedlater in claims. In addition, the display 3 displays a superposed imageto be mentioned later in detail. Further, a display screen of a carnavigation apparatus may be employed as the display 3.

The control unit 4 may be provided in a form of a microcomputer having aCPU, a ROM, a RAM, a backup RAM (no denotation in the drawing), and maycarry out various processes by executing various control programsmemorized in the ROM. The control unit 4 determines a position of theobstacle and a distance to the obstacle, based on the information of thetransmitted pulse signal and the information of the received pulsesignal output from the ultrasound wave sensors US1 to US4. The distanceto the obstacle is calculated based on the time between the transmissionand reception of the pulse signal. The position of the obstacle isdetermined based on which one of the four sensors transmitted the pulsesignal of the ultrasound wave and which one of the four sensors receivedthe signal. In this case, the position of the obstacle is put on one offour detection area axes of four sensors US1 to US4. Therefore, theinformation of the detection area axis serves as the information of theposition of the obstacle.

A relation between a detection area axis and determination of theposition of the obstacle is calculated as follows. The detection areaaxis is an axis that is established virtually to show a rough existenceposition of the obstacle in the captured image. In the presentembodiment, a center line of the directivity of each of the fourultrasound wave sensors and a center line of two overlapping detectionareas of adjacent sensors are used as the detection area axis. Thecenter line is, in this case, defined as both of the horizontal andvertical center of the sensor detection area.

More practically, the detection area axis is defined as illustrated inFIG. 2. That is, a detection area axis A1 is defined as a center line ofa detection area SA1 of the sensor US1, a detection area axis A2 isdefined as a center line of a detection area SA2 of the sensor US2, adetection area axis A3 is defined as a, center line of a detection areaSA3 of the sensor US3, and a detection area axis A4 is defined as acenter line of a detection area SA4 of the sensor US4. Further, adetection area axis CA1 is defined as a center line of an overlap of twoadjacent detection areas SA1 and SA2, which is denoted as an area SCA1,of two sensors US1 and US2. Likewise, a detection area axis CA2 isdefined as a center line of an overlap of two adjacent detection areasSA2 and SA3, which is denoted as an area SCA2, of two sensors US2 andUS3, and a detection area axis CA3 is defined as a center line of anoverlap of two adjacent detection areas SA3 and SA4, which is denoted asan area SCA3, of two sensors US3 and US4. In this case, the detectionareas SA1 to SA4 respectively correspond to the directivity of foursensors US1 to US4.

The determination of the position of the obstacle is performed in thefollowing manner. That is, when the ultrasound wave is transmitted fromthe ultrasound wave sensor US1 and the reflection wave is received bythe ultrasound wave sensor US1 with the magnitude of the reflection waveexceeding a threshold, the detection area axis A1 is determined as aselected axis. Further, when the ultrasound wave is transmitted from theultrasound wave sensor US1 and the reflection wave is received by theultrasound wave sensor US2 with the magnitude of the reflection waveexceeding a threshold, the detection area axis CA1 is determined as aselected axis, and, when the ultrasound wave is transmitted from theultrasound wave sensor US2 and the reflection wave is received by theultrasound wave sensor US1 with the magnitude of the reflection waveexceeding a threshold, it is also determined that the detection areaaxis CA1 is a selected axis.

Likewise, when the ultrasound wave is transmitted from the ultrasoundwave sensor US2 and the reflection wave is received by the ultrasoundwave sensor US2 with the magnitude of the reflection wave exceeding athreshold, the detection area axis A2 is determined as a selected axis.Further, when the ultrasound wave is transmitted from the ultrasoundwave sensor US2 and the reflection wave is received by the ultrasoundwave sensor US3, or vice versa, with the magnitude of the reflectionwave exceeding a threshold, the detection area axis CA2 is determined asa selected axis.

Further, the position detection by the sensors US3 and US4 is performedin the same manner as the position detection by the sensor US1, and therelation between the two adjacent sensors illustrated by the sensors US1and US2 is applied to a US2 to US3 relation and a US3 to US4 relation.

That is, when the ultrasound wave is transmitted from the ultrasoundwave sensor US3 and the reflection wave is received by the ultrasoundwave sensor US3 with the magnitude of the reflection wave exceeding athreshold, the detection area axis A3 is determined as a selected axis.Further, when the ultrasound wave is transmitted from the ultrasoundwave sensor US3 and the reflection wave is received by the ultrasoundwave sensor US4, or vice versa, with the magnitude of the reflectionwave exceeding a threshold, the detection area axis CA3 is determined asa selected axis.

Further, when the ultrasound wave is transmitted from the ultrasoundwave sensor US4 and the reflection wave is received by the ultrasoundwave sensor US4 with the magnitude of the reflection wave exceeding athreshold, the detection area axis A4 is determined as a selected axis.

The magnitude of the reflection wave may be determined as a peak heightof the received pulse wave, or may be determined as a width at a certainheight around the peak. In the following description, the peak height ofthe wave is used as the reflection wave magnitude. Further, thethreshold described above is used to filter a noise, that is, to pick upthe reflection wave caused only by the obstacle. The threshold may havea value that is arbitrarily determined according to the environment.More practically, when the transmission and reception of the wave areperformed by the same sensor, the threshold value may be set (a) todetect the obstacle around the sensor axis, that is, to detect theobstacle at the center of the detection area of the relevant sensor, and(b) not to detect the obstacle around the center axis of overlappingdetection areas of two adjacent sensors. Alternatively, when theultrasound wave is transmitted from one sensor and is received by anadjacent sensor, the threshold value may be set (a) to detect theobstacle around the center axis of the overlapping detection areas oftwo adjacent sensors, and (b) not to detect the obstacle around the axisof each of the two adjacent sensors.

The process to detect an obstacle is described in the following. Thatis, an obstacle detection process is explained with reference to a flowin FIG. 3. The process is conducted under control of the control unit 4.The process detects the obstacle either by using a single sensor thatsends and receives the ultrasound wave and its reflection wave, or byusing two sensors, one of which sends the wave and the other receivesthe reflection. In other words, for each of the four sensors and foreach of the combination of two sensors, the above-described sensingprocess is applied according to the flow in FIG. 3.

The flow of the process starts at, for example, a gear shift intoReverse (“R”) position, which is detected by a gear shift sensor or thelike.

Then, in step S1, the process performs an initialization, and proceedsto step S2. In step S2, wave transmission from the ultrasound sensor isperformed by the sensor. The transmission of the ultrasound wave fromeach of the ultrasound wave sensors US1 to US4 has a regular interval sothat the wave from different sensors does not overlap with each other.

Then, in step S3, the reflection wave of the ultrasound wave transmittedby the ultrasound wave sensor is received. In this case, the wavetransmitted by the sensor US1 may is received by either of the sensorUS1 or US2. Therefore, the flow in FIG. 3 is applied for both cases,that is, reception of the wave by the sensor US1, and by the sensor US2.

Then, in step S4, threshold setting and max count setting of the counterare performed. The threshold in this case is the value described abovefor the signal noise distinction. Therefore, in step S4, the thresholdvalue may be respectively different for the wave reception by the samesensor and the wave reception by the different sensor. Thus, thethreshold values of sensors US1 to US4 may respectively different fromeach other. The counter counts the number of repetition of the abovedetermination, that is, the wave transmission, the wave reception, andsignal intensity comparison relative to the threshold (described later).The max count of the counter is set to limit the repeating number of thedetermination for the required accuracy. That is, by repeating the abovedetermination at least for the number of times of the max count, thereceived pulse signal can securely determined as the reflection wavefrom the obstacle. The number of the max count may, for example, be setto 3.

Then, in step S5, the peak height of the received pulse signal isdetermined to be exceeding the threshold. If it is determined asexceeding the threshold (step S5, Yes), the process proceeds to step S7.If not (step S5, No), the process proceeds to step S6.

Then, in step S6, the max count as well as the counted value of thecounter is cleared, and “void” data is stored in the storage device 5 asdistance data that represents the distance to the obstacle. Then, theflow returns to step S2 for repeating the process.

Then, in step S7, based on information of the transmitted wave and thereceived wave, the distance to the obstacle is calculated.

Then, in step S8, the counted value of the counter is incremented byone, to proceed to step S9.

Then, in step S9, whether or not the counted value of the counter hasreached the max count is determined. If it is determined as max count(step S9, Yes), the process proceeds to step S11. If not (step S9, No),the process proceeds to S10.

Then, in step S10, the transmission and reception of the ultrasound waveare performed again before returning to step S5, to repeat the followingprocess.

In step S11, the distance data is stored in the storage device 5, andthe process returns to step S2. The distance data is stored for each ofthe detection area axes. For example, the distance data for the wavetransmission and reception by the same sensor US1 is associated withinformation of the detection area axis A1 in the storage device 5.Alternatively, the distance data for the wave transmission by the sensorUS1 and the wave reception by the sensor US2 is associated withinformation of the detection area axis CA1 in the storage device 5. Thatis, in other words, once the obstacle is detected by the sensor, thedistance data of the detected obstacle is continually acquired over acertain time period, and is stored in the storage device 5 together withthe detection area axis information. Therefore, the control unit 4functions as data acquisition unit mentioned later in the claims.

The distance data is stored in the storage device 5 every time theabove-mentioned set of wave transmission cycle is executed. If anobstacle is detected in the present set of cycle, the distance data andthe detection area axis information are stored. If no obstacle isdetected in the cycle, information indicative of non-existence of datais, for example, stored.

In the above description, the threshold and max count setting in step S4is performed after step S3 where the reflection wave is received.However, the threshold and max count setting may be performed prior tothe reception of the reflection wave, or may be performed at the sametime of initialization in step S1. Further, the threshold and max countsetting may take the noise condition into account.

This flow of FIG. 3 is concluded when the gear is shifted to a differentposition from the reverse position (R), which is detected by the gearshift sensor or the like.

The storage device 5 stores detection data (i.e., the distance data ofthe obstacle and the information of the detection area axis) acquired bythe control unit 4 continually over time in an electrically re-writablememory area in a cumulative manner. Therefore, the storage device 5functions as a storage unit mentioned later in the claims. In addition,the detection data is accumulated for the past several cycles ofdetection process in the storage device 5, and the oldest detection datais erased for the storage of the new detection data.

When the obstacle is detected, the control unit 4 performs a superposingdisplay process. The flow of the process is illustrated in FIG. 4. Theprocess is started when, for example, a gear is shifted to Reverse (“R”)position, which is detected by the gear shift sensor or the like.

In step S21, data of the captured image at the moment is acquired fromthe camera 2.

Then, in step S22, information for the past several cycles is retrievedfrom the storage device 5. In the present embodiment, the informationfor five detection cycles is retrieved. More practically, for the sevendetection area axes of A1 to A4 and CA1 to CA3, the information for fivedetection cycles is retrieved.

Then, based on retrieved information for the past five cycles, themovement of the obstacle relative to the own vehicle (designated as an“obstacle condition” in the following) is determined in step S23. Morespecifically, if the latest information in the storage device 5 is aboutthe distance to the obstacle and the detection area axis, whether theobstacle is getting closer, getting farther, or stopping is determinedbased on the retrieved information of the distance to the obstacle overtime. If the information of non-existence of data is stored for the pastfive cycles in the storage device 5, the obstacle condition is notdetermined.

Then, in step S24, a parking process is performed. In the markingprocess, a mark to be displayed in a superposing manner on those sevenaxes of A1 to A4 and CA1 to CA3 is determined based on the informationregarding the obstacle condition from the past five cycles. The markedaxis determined based on the detection area axis information retrievedfrom the storage unit 5. Further, the marks respectively representingeach of the past five cycles of detection are arranged on the selectedaxis according to the detected distance of the distance data.Furthermore, the color of the marks is determined either as red, blue,or yellow or the like, depending on the obstacle condition. That is, ifthe obstacle is getting nearer to the own vehicle, the mark may bepresented in red, or in a “danger” color. If the obstacle is gettingfarther from the own vehicle, the mark may be presented in blue, or in a“safe” color. If the obstacle is not moving relative to the own vehicle,the mark may be presented in yellow, or in a “neutral” color. Inaddition, the size of the mark is changed in proportion to the “oldness”of the distance data. That is, the older the distance data (i.e., thedetection data) is, the smaller the size of the mark becomes. Further,the transparency of the mark is also changed in proportion to the“oldness” of the data. That is, the older the distance data (i.e., thedetection data) is, the more transparent the mark becomes. When thelatest information indicates “void” data for a certain detection areaaxis, the mark for that detection area axis is not displayed.

Then, in step S25, the mark processed in step S24 is superposed on thecaptured image, and the data of the “superposed” image is output to thedisplay 3. The process then returns to step S21 to repeat the flow. Thesuperposing of the mark is performed in a well-known conventionalmanner. The display 3 then displays the superposed image according tothe data.

This flow of FIG. 4 is concluded when the gear is shifted to a differentposition from the reverse position (R), which is detected by the gearshift sensor or the like.

In summary, the control unit 4 controls how the mark is displayedaccording to the detection data based on the multiple records of data.That is, the “oldness” or “newness” of the data is represented in thesuperposed image, by changing sizes, positions and the like, so that thedistinction of the “oldness” of the data is apparent in the image.Therefore, the control unit 4 functions as a change unit mentioned laterin the claims.

With reference to FIG. 5 to FIG. 7C, the above-mentioned superposedimage is described. The superposed image is displayed on the display 3in the following manner. That is, FIG. 5 is an illustration of thedetection area axes of A1 to A4 and CA1 to CA3 virtually superposed onthe captured image, and FIGS. 6A to 7C are illustrations of the markssuperposed in the captured image. In the present embodiment, the marksin the image have an oval shape.

The marks in the image are positioned along the axes A1 to A4 and CA1 toCA3 as shown in FIG. 5. The lines representing those seven axes in FIG.5 are drawn for explanation purposes, and are not displayed in thesuperposed image in the present embodiment. The axes may be displayed inthe superposed image.

In case that the obstacle is getting nearer to the own vehicle, themarks in the image become bigger and less transparent on the own vehicleside as shown in FIG. 6A. Further, when the obstacle is moving sidewaysrelative to the own vehicle, the moving direction of the obstacle isindicated by the bigger and less transparent marks as shown in FIG. 6B.The viewpoint of the superposed image may be the one in FIG. 6A, whichis the same viewpoint as the captured image, or may be the one in FIG.6B, which is a vertically-looking down view from above after a viewpointconversion. If the obstacle is detected in the directions of more thanone detection area axis, the marks are displayed in the manner as shownin FIG. 6C. The viewpoint of the image in FIG. 6C is the same viewpointof the captured image. The obstacle detection in the multi detectionareas are described in more detail as the explanation of FIGS. 7A to 7Cin the following.

Further, when the obstacle is a wide object such as a wall or the like,the marks are arranged along a couple of axes of multiple detectionareas, as shown in FIG. 7A to FIG. 7C. In this case, FIG. 7A is anillustrative example of the superposed image when the own vehicle isgetting closer to the wall, and FIG. 7B is an illustrative example ofthe superposed image when the own vehicle is stopping in front of thewall, and FIG. 7C is an illustrative example of the superposed imagewhen the own vehicle is getting farther away from the wall. In addition,the superposed images shown in FIG. 7A to FIG. 7C are bird's eye views.

The operation scheme of the field watch apparatus of the presentinvention is now summarized as follows. That is, by the changing sizesand transparency of the marks in the superposed image, the respectivemarks are distinguished, in terms of which mark is older than the other,in a self-explanatory manner, based on the detection data of theobstacle that is detected by the obstacle sensor 1 (i.e., the ultrasoundwave sensors US1 to US4). The above distinction of the “oldness” of theobstacle marks thus enables the viewer to recognize how the obstacle ismoving relative to the own vehicle, as the vehicle moves, or, in otherwords, as the obstacle in the image moves over time. That is, when theobstacle is getting closer to the vehicle, the marks on the vehicle sidein the captured image are displayed in a larger size, to good effect ofrepresenting that the obstacle is approaching to the vehicle.Alternatively, when the obstacle is moving away from the vehicle, themarks on the vehicle side in the captured image is displayed in asmaller size, to good effect of representing that the obstacle isdeparting from the vehicle. By the change of the transparency of themarks in the image, the above effect of approaching and departing can bestrengthened. Therefore, the direction of the obstacle movement isvisually represented by those marks changing in size and otherattributes. As a result, the viewer can intuitively understand which waythe obstacle is moving relative to the own vehicle as well as obtaininga feel of how large the actual size of the obstacle is.

Further, according to the above-mentioned operation scheme, the marksare displayed along one axis or multiple axes according to the detecteddistance of the obstacle, based on the reflection of the ultrasound wavereceived by the respective sensors US1 to US4. In addition, the positionof those detection area axes in the image is stable and fixed, once thesensors and the camera 2 are fixedly installed on the vehicle.Therefore, the display area of the marks may be limited to a certainportion of the captured image without compromising the above-describedadvantageous effects of intuitively representing the movement directionof the obstacle as well as the size of the obstacle. In addition, thedisplay used in the vehicle usually has a smaller size such as 6.5inches to 8 inches or the like, thereby allowing the above-describedlimitation of the mark display area to a certain portion in the imagewithout having a trouble such as the display of the marks and thecaptured obstacle in the image being too distant from each other. As aresult, the process load of the present operation scheme is reducedrelative to a process that calculates an accurate position of theobstacle based on the captured image and displays the marks accuratelyat the calculated positions. In other words, the advantageous effects ofintuitively displaying the obstacle movement can be achieved by thereduced amount of processing.

Although the present disclosure has been fully described in connectionwith preferred embodiment thereof with reference to the accompanyingdrawings, it is to be noted that various changes and modifications willbecome apparent to those skilled in the art.

For example, reception level of the reflection wave may be calculated.That is, between steps S4 and S5 in FIG. 3, or as step S5 shown in FIG.8, the peak height of the received pulse signal that is received in stepS3 in FIG. 8 may be calculated. The reception level of the signal may bedetermined at a certain height of the pulse signal. This levelcalculation may be performed prior to step S4 in FIG. 8.

Then, the reception level may be stored in the storage device 5 in stepS12 in FIG. 8 together with the distance data. The association of thereception level with the detection area axis may be performed in thesame manner as the association of the distance data.

Further, the reception level may be used to change the mark size. Thatis, for example, higher reception level may be represented by the largermark size in the image. The size table to determine the mark sizeaccording to the reception level may be employed for the display of themark in the image. The mark size may be controlled so that the marks attwo adjacent positions do not overlap with each other.

Furthermore, the mark size may be determined by combining two or morefactors. That is, for example, the reception level and the “oldness” ofthe detection data may be combined to determine the mark size in theimage. The transparency may also be employed for representing the“oldness” of the data.

When the obstacle reflects the electro-magnetic wave or the sound wave,the magnitude of the reflection wave from the obstacle is basically inproportion to the size and the distance of the obstacle. Therefore, theobstacle marks sized to be proportional to the reception level of thereflection wave (e.g., the magnitude of the wave, or the signalintensity of the reflection wave) can accurately represent the size ofthe obstacle in the near field of the vehicle. In other words, when theobstacle is marked in the captured image in the above-described manner,the user can easily recognize the size of the obstacle based on thenovel arrangement of the obstacle marks in the present embodiment.

Further, though the older marks are made smaller and more transparent inthe present embodiment, a different mark display scheme may be employed.That is, for example, only the size change or transparency change may beused to represent the older marks in the superposed image, for thepurpose of the obstacle movement direction.

Further, the color change (i.e. at least one of hue, saturation, andbrightness of the mark) may be employed to represent the obstaclemovement. More practically, the closer mark relative to the own vehiclemay have the hue of the more “dangerous” color, or higher saturationintensity, or brighter color. Alternatively, the farther marks may havethe “safer” color, or lower saturation intensity, or less brighter colorand the like. Furthermore, the color as well as other factors of sizeand transparency may be combined to represent the obstacle movement.

Further, determination of the obstacle condition determined by thecontrol unit 4 may be omitted, and color change of the mark, such as thehue change, for representing the relative movement of the obstacle maynot be used.

Further, mark shape may be arbitrarily changed. That is, not only theoval shape but also other shapes such as a round shape, a rectangularshape, a star shape, a polygonal shape or the like may be used.

Further, the number of the ultrasound sensors may be different from fourthat is used in the present embodiment. The number of the sensors may begreater than four, or smaller than four.

Further, the camera 2 may be installed to capture a front image of theown vehicle, and the obstacle sensor 1 may be installed to detect anobstacle in the front field of the vehicle. Alternatively, the camera 2may be used to capture a surrounding field image and/or a side fieldimage of the own vehicle, and the obstacle sensor 1 may be used todetect an obstacle in the surrounding field and/or side field of the ownvehicle. Furthermore, the front and side field image and the rear fieldimage may be combined to generate the superposed image.

Further, the ultrasound wave sonar used as the obstacle sensor 1 in thepresent embodiment may be replaced with other sensors, such as amillimeter wave radar, a laser radar or the like. Furthermore, the imagerecognition technique to recognize the obstacle in the captured imagemay be used as the obstacle sensor 1.

Such changes, modifications, and summarized operation schemes are to beunderstood as being within the scope of the present disclosure asdefined by appended claims.

1. A field watch apparatus comprising: an image capture unit forcapturing a field image around a vehicle; an obstacle detector fordetecting an obstacle around the vehicle; a display unit for displayingthe field image captured by the image capture unit, wherein the fieldimage has an obstacle mark superposed thereon when the obstacle isdetected by the obstacle detector; a data acquisition unit forcontinually acquiring obstacle data from the obstacle detector after aninitial detection of the obstacle; a storage unit for accumulating theobstacle data continually acquired by the data acquisition unit; and achange unit for changing the obstacle mark in association with theobstacle data, wherein the change unit displays multiple obstacle markson the field image based on multiple pieces of the obstacle data in thestorage unit, and the obstacle mark representing an older piece ofobstacle data is changed from the obstacle mark representing a lessolder piece of obstacle data for the ease of distinction in the fieldimage.
 2. The field watch apparatus of claim 1, wherein the obstacledata includes information on a position and a distance to the obstaclethat is detected by the obstacle detector.
 3. The field watch apparatusof claim 1, wherein the obstacle mark is made smaller for the olderpiece of obstacle data.
 4. The field watch apparatus of claim 1, whereinthe obstacle mark is made more transparent for the older piece ofobstacle data.
 5. The field watch apparatus of claim 1, wherein at leastone of hue, saturation, and brightness of the obstacle mark is changedfor the distinction of respective pieces of obstacle data.
 6. The fieldwatch apparatus of claim 2, wherein the obstacle detector is made upfrom multiple distance sensors having respectively different detectionareas, the change unit controls the display of the obstacle marks to bealigned along a detection axis of the respective distance sensorsaccording to the detected distance of the obstacle, and the display ofthe obstacle mark is determined respectively for each of the detectionaxes of the multiple distance sensors based on the detection of theobstacle by the respective sensors.
 7. The field watch apparatus ofclaim 6, wherein the change unit uses additional detection axes thatdefine a center line of two detection axes of adjacent distance sensorsfor the display of the obstacle mark according to the detected distanceof the obstacle.
 8. A field watch apparatus comprising: an image captureunit for capturing a field image around a vehicle: an obstacle sensorfor detecting an obstacle around the vehicle by using reflection of oneof electro-magnetic wave and sound wave; a display unit for displayingthe field image captured by the image capture unit, wherein the fieldimage has an obstacle mark superposed thereon when the obstacle isdetected by the obstacle sensor; and a change unit for changing theobstacle mark according to the magnitude of the reflection wave detectedby the obstacle sensor.
 9. The field watch apparatus of claim 8 furthercomprising: a data acquisition unit for continually acquiring obstacledata from the obstacle sensor after an initial detection of theobstacle; and a storage unit for accumulating the obstacle datacontinually acquired by the data acquisition unit, wherein the changeunit displays multiple obstacle marks on the field image based onmultiple pieces of the obstacle data in the storage unit, the obstaclemark representing an older piece of obstacle data is changed from theobstacle mark representing a less older piece of obstacle data for theease of distinction in the field image, and the size of the obstaclemark is made to be in proportion to the magnitude of the reflection wavedetected by the obstacle sensor that has detected the obstacle.
 10. Thefield watch apparatus of claim 8, wherein the obstacle data includesinformation on the magnitude of the reflection wave as well as aposition and a distance to the obstacle that is detected by the obstaclesensor.
 11. The field watch apparatus of claim 8, wherein the obstaclemark is made smaller for the older piece of obstacle data.
 12. The fieldwatch apparatus of claim 8, wherein the obstacle mark is made moretransparent for the older piece of, obstacle data.
 13. The field watchapparatus of claim 8, wherein at least one of hue, saturation, andbrightness of the obstacle mark is changed for the distinction ofrespective pieces of obstacle data.
 14. The field watch apparatus ofclaim 10, wherein the obstacle sensor is made up from multiple distancesensors having respectively different detection areas, the change unitcontrols the display of the obstacle marks to be aligned along adetection axis of the respective distance sensors according to thedetected distance of the obstacle, and the display of the obstacle markis determined respectively for each of the detection axes of themultiple distance sensors based on the detection of the obstacle by therespective sensors.
 15. The field watch apparatus of claim 14, whereinthe change unit uses additional detection axes that define a center lineof two detection axes of adjacent distance sensors for the display ofthe obstacle mark according to the detected distance of the obstacle.